We propose to continue to prepare and distribute pure human erythropoietin and to study possible improvements in fractionating methods. These improvements may include affinity chromatography using lectins and/or monoclonal anti-erythropoietin, as well as high pressure liquid chromatography. We will also study possible alternative large scale sources of erythropoietin, such as kidney extraction and cell culture methods. We will use the newly developed radioimmunoassay for screening. Successful erythropoietin production in cell culture may also permit study of its biogenesis and regulation. Improvement in the specificity of the radioimmunoassay will also be studied. We will continue to work on finding a method for radioiodination of erythropoietin with retention of biological activity, and to use such labeled material for the study of physiological properties. Simultaneously, we will continue the investigation of the chemical properties of erythropoietin with the intention of understanding the structural requirements for its biological activity, as a pre-requisite for its eventual synthesis.